Project objectives center on light and electron microscopic analyses of the chromosome complements of prosimian primates housed at the Duke University Primate Center. To date, mitotic karyotypes of species and hybrdis of the genus Lemur have been established by light microscopy of G-banded chromosomes, and analyzed at meiosis by synaptonemal complex (SC) karyotyping of surface spread pachytene spermatocytes. From banding studies it is concluded that Robertsonian fusion of acrocentric chromosomes has been the principal mode of karyotypic change in Lemur evolution. Thus the primary karyotyptic differences found among Lemur species are in the combinations of acrocentrics forming Robertsonian metacentrics. These findings have led to proposed reconstructions of Lemur phylogeny. In specific instances our interpretations have been supported by the confirmation of homology through SC analysis in hybrids. To test the principles derived from the Lemur study, analyses are being extended to comparisons of more distantly related genera. The ultimate aim is to reconstruct probably lines of phyletic divergence among other prosiminans in particular, and primates in general. A screening program is designed to provide a pool of essential karyotypic data, which will also be available to other investigators. On the basis of preliminary observations, karyotypic variants within species and subspecies are expected to be found in the banding information from the survey of the large population. Robertsonian fusions will be examined by SC analysis, particularly in heterozygotes (hybrids) as in Lemur, while major variations in heterochromatin (C-bands) and nucleolus organizer region (NOR) patterns will be studied in mitotic and meiotic chromosomes in order to understand their signficance, their inheritance, and their specific effects on phylogenetic relationships.